Two separate computers stutter at the exact same time

My girlfriend's desk and my desk are side by side. We share the same power feed from the basesment, we are both hardwired to the same modem for internet.

Our computers will randomly stutter a few times per day, at the exact same time for the exact same length of time. The mouse lags hard, the audio stutters, video stutters, everything just stutters. Lasts about 1-2 seconds. Happens whether we are in games, or watching twitch, or doing separate things. Even happens when one of us is not at the computer.

Any idea what might be going on? I cant imagine a power surge or something as we have completely different hardware and good power supplies. Power or internet doesn't flicker or anything. Some sort of electromagnetic pulse? Aliens?

Thanks

Edit: This started happening at the same time for both of us, a couple of weeks ago.